Computed tomography (CT) scan produces cross-sectional images of the body lying in a cylinder-shaped large machine equipped with an X-ray generator, and enables a user to more clearly see structures and lesions due to less overlap of structures than a regular X-ray. Therefore, CT scans have been widely used for examination of most of organs and diseases.
Sufficient image quality (resolution or precision) is very important for an accurate diagnose of the disease with CT scans. Along with the advancement of the CT hardware technologies, much efforts are underway to improve the quality of CT images. Examples of the efforts may include the multi-channel detector technology and high-speed high-resolution imaging technology. Usually, the efforts to improve a quality of a CT image involve high-dose radiation exposure and thus may cause an increased cancer risk to patients. Particularly, considering the recent public awareness of radiation exposure, the efforts to acquire a high-quality diagnostic image need to be accompanied by efforts to minimize the radiation dose.
In an effort to do so, CT scanner manufacturers have released iterative reconstruction CT systems which enable to produce noise-reduced CT images at lower radiation dose. However, it is often not easy to afford the iterative reconstruction CT systems due to higher expenses than conventional products and difficulty in disposal of the conventional products. The CT scanner manufacturers sometimes offer an upgrade program to convert the legacy CT systems into in the iterative reconstruction CT systems. However, those upgrade programs are not applicable to all legacy CT systems due to technical problems and high cost. The present invention was devised to provide a solution to these problems. A background technology of the present invention is disclosed in Korean Patent Laid-open Publication No. 10-2014-0130784.